Hollow airfoils (e.g. fans, blades or vanes) for use in gas turbine engines are known.
For example, hollow metallic fan blades have been in operation for many years and also hollow metallic guide vanes. GB2147055A discloses such a hollow metallic airfoil.
GB2154286A discloses a hollow composite airfoil in which a process for forming the airfoil using carbon, graphite or glass reinforced epoxy resin composites is proposed. The airfoil has an outer shell producing the airfoil surfaces and a corrugated internal support. The shell is formed from stacked assemblies of laminae, one stack for each side of the airfoil and are joined to each other at the leading and trailing edge of the airfoil. A boot at one end of the airfoil and a mounting platform at the other end of the airfoil seal off the interior of the airfoil from the exterior.